Chocolate chips in cookies are not blighted by the unappealing fat bloom experienced in conventional chocolate, but the industry is still at odds as to why after a study funded by the International Organization of Confectioners (PMCA) proved inconclusive.

Fat bloom can appear as a white film on the surface of chocolate when oil creates recrystallization of some cocoa butter triglycerides, causing the chocolate to be less appealing to consumers.

The study recently published in the journal Food Research International asked why chocolate chips in cookies exhibited less bloom despite being subjected to sufficient heat to melt and break temper of the chocolate.

Unknown reason

The authors hypothesized that fat migration from the cookie dough into the chocolate chip during baking would disrupt cocoa butter crystallisation when cooled, thus restricting bloom.

They found that while this sensation played some part, it did not give a full explanation and other ingredients in the cookie dough must also be responsible for bloom prevention .

“Although fat migration clearly contributes to bloom inhibition …the exact mechanism behind this inhibition is still unknown,” said the study

“Based on the soft texture of chocolate chips in cookies after baking, we speculate that the phase behaviour and change in crystallization/ polymorphism of the mixed fat system is responsible for bloom inhibition.”

“Perhaps the complex fat mixture in the chocolate chip after baking does not undergo polymorphic transformations thought to be responsible for bloom,” it continued.

The authors concluded that further work in the area was warranted.

Method & analysis

The study reached its conclusions by baking and cookies a sand fat model system at different levels and types of fat in the matrix.

Under the sand fat model system, chocolate chips were baked in cups filled with mixtures of fat and washed sea sand to mimic the effect of fat in cookie dough on chocolate chips in the absence of other ingredients.

The researchers evaluated bloom after 10 days using a microscope.

All fats, expect cocoa butter, were found to inhibit bloom when fat levels were high.

Cookies containing palm oil and olive oil required a minimum of 16% fat migration to help prevent bloom, otherwise bloom could occur, said the study.

However, it also found that a higher level of fat migration was required in the sand model system, meaning other ingredients must also play a role in bloom prevention.

ADM cocoa was acknowledged for its assistance in conducting the analysis. PMCA was the main funder. Its members include Blommer Chocolate and Mars.

Chocolate chips in cookies are not blighted by the unappealing fat bloom experienced in conventional chocolate, but the industry is still at odds as to why after a study funded by the International Organization of Confectioners (PMCA) proved inconclusive.